What is NOT a main stitch used in knitting?

The plain stitch is not recognized as a main stitch used in knitting terminology. In knitting, the primary stitches are the knit stitch and the purl stitch. The knit stitch involves inserting the needle into the front of the stitch and looping the yarn around to create a new stitch, while the purl stitch is worked by inserting the needle into the back of the stitch and pulling the yarn through, which results in a textured, opposite-facing stitch.

Understanding the fundamental techniques is crucial for anyone learning to knit, as each stitch builds the foundation for creating various patterns and textures in knitting projects. The other options represent essential stitches that every knitter should be familiar with, making plain stitch an inaccurate description of a primary knitting technique.